Project Summary/Abstract With the original grant (R01 HD051498), we developed, field-tested, and validated the Individualized Classroom Assessment Scoring System (inCLASS), an observational assessment of a child's behavioral engagement with teachers, peers, and tasks within pre-k and kindergarten (K) classrooms. Justification for this work rested on evidence that children's interactions with peers, teachers, and instructional activities in pre-k were proximal mechanisms contributing to their social, mathematics, language, and literacy learning. As such, a direct assessment of children's classroom engagement provides essential information as to how children actually develop school readiness skills. We propose this competitive renewal as the pressing next step in a line of work with the inCLASS observational tool to understand how the interplay between children's engagement and their executive functions (EF) contribute to school readiness and K school performance, beyond the role of individual differences and home experiences children bring with them to pre-k. The aims of this longitudinal observational study are to: 1) Examine how children's engagement and EF relate to one another during pre-k. We hypothesize that engagement and EF will have a positive, reciprocal association with each other over time, with EF serving as the leading indicator; these links will be stronger under conditions of high classroom quality. 2) Determine the extent to which children's engagement and EF contribute to development of more distal readiness skills and school performance. The repeated measures, longitudinal design will permit us to examine mechanisms by which engagement and EF facilitate school readiness skill development and later K school performance. In particular, we expect engagement will mediate the links between children's EF and the more distal child outcomes. 3) Examine the role of classroom quality (e.g., teacher-child interactions, time spent on literacy instruction) over time. We anticipate classroom quality indicators having a positive direct effect on children's EF, behavioral engagement, readiness skills, and school performance, while also hypothesizing that classroom quality will moderate the links between children's engagement and EF, and the development of readiness skills and school performance We propose a longitudinal study of 100 pre-k teachers and 800 pre-k children and their primary caregivers, with follow-up of children into 200 K classrooms. Within each pre-k classroom, eight children will be randomly selected for assessments of school readiness (language, literacy, mathematics, social skills) in the fall and spring of the pre-k and K years, with supplemental K school performance data collected from school archives. Assessments of behavioral engagement and classroom quality will be obtained through repeated live observations, whereas EF will be measured during repeated direct assessments (all across both years). The knowledge gained from this examination of how children's engagement and EF interact with classroom quality will inform our understanding of how pre-k programs can impact children's school readiness.